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OpenStem
@openstem · Joined Jul 2026
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Flashcards10 cards
Why do living things need to make new cells at all?1 / 10
Cells divide to help a body grow bigger, to repair damage, and to replace cells that wear out or die. Without new cells, living things could not grow, heal, or keep working properly.
Biology · L2 · Why Cells Divide
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Biology · L2 · Why Cells DivideFlashcards10 cards
What is mitosis, in simple terms?1 / 10
Mitosis is the basic process by which one cell divides to make two new cells that are identical to each other and to the original cell. It is how your body grows and repairs itself.
Biology · L2 · The Simple Steps of Cell Division (Mitosis)
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Biology · L2 · The Simple Steps of Cell Division (Mitosis)Flashcards9 cards
What is melanin?1 / 9
Melanin is a natural pigment — a substance that gives color — made by cells in the skin. It's the main reason skin has the color it does, and it also colors hair and the iris of the eye.
Biology · L2 · What Is Melanin?
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Biology · L2 · What Is Melanin?Flashcards9 cards
Besides giving skin its color, what is one important job melanin does?1 / 9
Melanin helps protect skin from the sun. It absorbs and scatters ultraviolet (UV) radiation from sunlight, which reduces the damage UV rays can do to skin cells.
Biology · L2 · Melanin: Sun Protection and Inheritance
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Biology · L2 · Melanin: Sun Protection and InheritanceFlashcards10 cards
What are the three main types of vaccines described here?1 / 10
Weakened (live-attenuated) vaccines, inactivated (killed) vaccines, and mRNA vaccines — three different ways scientists teach your immune system to recognize a germ.
Biology · L2 · The Three Main Types of Vaccines
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Biology · L2 · The Three Main Types of VaccinesFlashcards9 cards
Which of the three vaccine types uses a living germ that has simply been made very weak?1 / 9
The weakened, or live-attenuated, vaccine.
Biology · L2 · Comparing How Vaccines Are Made
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Biology · L2 · Comparing How Vaccines Are MadeFlashcards10 cards
What is actually stored inside a camel's hump?1 / 10
Fat — not water. The hump is made of fatty tissue that the camel's body can break down for energy when food is scarce.
Biology · L2 · Camels: Fat Storage and Fast Rehydration
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Biology · L2 · Camels: Fat Storage and Fast RehydrationFlashcards10 cards
What is a kangaroo rat?1 / 10
A small desert rodent, native to the deserts of North America, that hops on its long back legs like a tiny kangaroo and is famous for never needing to drink water.
Biology · L2 · Kangaroo Rats and Nighttime Survival
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Biology · L2 · Kangaroo Rats and Nighttime SurvivalFlashcards10 cards
What is an antigen?1 / 10
An antigen is a marker — usually a protein — found on the surface of a germ or other invader. It's what your immune system uses to recognize that something doesn't belong in your body.
Biology · L2 · Antibodies: The Lock-and-Key Idea
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Biology · L2 · Antibodies: The Lock-and-Key IdeaFlashcards10 cards
What does it mean for an antibody to "mark" an invader?1 / 10
When an antibody sticks to an antigen, it acts like a flag or a tag, showing the rest of the immune system exactly which invader needs to be destroyed.
Biology · L2 · How Antibodies Mark Invaders for Destruction
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Biology · L2 · How Antibodies Mark Invaders for DestructionFlashcards10 cards
Why do plants need a way to protect themselves?1 / 10
Plants cannot run away from hungry animals or from people who might step on or pick them. Instead, many plants protect themselves by being unpleasant to touch or eat — spiky, stingy, itchy, or bitter — so animals learn to leave them alone.
Biology · L2 · Meet the Plants That Fight Back
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Biology · L2 · Meet the Plants That Fight BackFlashcards10 cards
What do poison ivy leaves look like?1 / 10
Poison ivy grows in groups of three shiny, pointed leaves. There's an old saying that helps people remember: "Leaves of three, let it be."
Biology · L2 · Spotting Plant Defenses in the Wild
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Biology · L2 · Spotting Plant Defenses in the WildFlashcards10 cards
What is a neuron?1 / 10
A neuron is a nerve cell — a special cell built to receive a message, carry it along, and pass it on to the next cell. Neurons are the basic building blocks of the whole nervous system.
Biology · L2 · Meet the Neuron
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Biology · L2 · Meet the NeuronFlashcards10 cards
What is a synapse?1 / 10
A synapse is the tiny gap between the axon terminal of one neuron and the dendrite of the next neuron. Neurons never actually touch — the message has to cross this gap.
Biology · L2 · Crossing the Synapse
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Biology · L2 · Crossing the SynapseFlashcards9 cards
What does it mean when scientists say they've 'discovered' a new species?1 / 9
It means they've found a living thing that doesn't match any species already described in science. It might be totally unknown, even if people living nearby have known about it for generations.
Biology · L2 · Discovering a New Species
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Biology · L2 · Discovering a New SpeciesFlashcards9 cards
What is a scientific name made of?1 / 9
A scientific name has two parts: the genus name first, then the species name. This two-part system is called binomial nomenclature — 'binomial' simply means 'two names.'
Biology · L2 · The Two-Part Scientific Name
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Biology · L2 · The Two-Part Scientific NameFlashcards7 cards
Match the scientific name to the animal: Canis lupus.1 / 7
The gray wolf.
Biology · L2 · Practice: Match the Species Name
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Biology · L2 · Practice: Match the Species NameFlashcards9 cards
What is the nucleus, and what two roles does it play in a eukaryotic cell?1 / 9
The nucleus is the cell's control center. It stores the cell's DNA, organized with proteins into chromatin, and it directs gene expression — deciding which genes are switched on to produce which proteins. It is bounded by a double membrane called the nuclear envelope.
Biology · L3 · Organelle Structure and Function
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Biology · L3 · Organelle Structure and FunctionFlashcards9 cards
What is diffusion, and why does it require no energy input from the cell?1 / 9
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, until the concentration is equal throughout (equilibrium). It is driven by the random, constant motion of particles, so it is a form of passive transport that needs no ATP from the cell.
Biology · L3 · Membrane Transport and the Cell Cycle
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Biology · L3 · Membrane Transport and the Cell CycleFlashcards10 cards
What is an allele?1 / 10
An alternative version of a gene. Alleles occupy the same location (locus) on homologous chromosomes and can produce different versions of the same trait, such as purple or white flower color.
Biology · L3 · Mendelian Genetics Vocabulary
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Biology · L3 · Mendelian Genetics VocabularyFlashcards9 cards
What is a Punnett square used for?1 / 9
A grid-based diagram that predicts the possible genotype and phenotype combinations among offspring of a genetic cross, by pairing every possible gamete from one parent with every possible gamete from the other.
Biology · L3 · Punnett Squares and Inheritance Patterns
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Biology · L3 · Punnett Squares and Inheritance PatternsFlashcards10 cards
What does DNA stand for, and what is its primary role in cells?1 / 10
Deoxyribonucleic acid — it stores the genetic instructions used in the development, functioning, and reproduction of living organisms.
Biology · L3 · DNA Structure
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Biology · L3 · DNA StructureFlashcards10 cards
What does it mean that DNA replication is 'semi-conservative'?1 / 10
Each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.
Biology · L3 · DNA Replication
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Biology · L3 · DNA ReplicationFlashcards10 cards
What is natural selection?1 / 10
The process by which individuals with heritable traits better suited to their environment survive and reproduce at higher rates, passing those traits to offspring. It is a mechanism of evolution, not evolution itself.
Biology · L3 · Mechanisms of Evolution
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Biology · L3 · Mechanisms of EvolutionFlashcards10 cards
What does the fossil record show about evolution?1 / 10
A chronological sequence of preserved remains in rock strata that documents how species have changed over time, including transitional forms that share features of both ancestral and descendant groups.
Biology · L3 · Evidence for Evolution and Speciation
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Biology · L3 · Evidence for Evolution and SpeciationFlashcards10 cards
What are the four chambers of the human heart?1 / 10
Two upper chambers, the right atrium and left atrium, and two lower chambers, the right ventricle and left ventricle. The atria receive blood; the ventricles pump it out under pressure.
Biology · L3 · Heart Anatomy and the Cardiac Cycle
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Biology · L3 · Heart Anatomy and the Cardiac CycleFlashcards10 cards
How is the structure of an artery wall suited to its function?1 / 10
Artery walls are thick, muscular, and elastic. This lets them withstand the high pressure of blood surging directly from the heart and stretch with each pulse, helping push blood onward.
Biology · L3 · Blood Vessels and Blood Composition
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Biology · L3 · Blood Vessels and Blood CompositionFlashcards10 cards
What happens to air as it passes through the nasal cavity?1 / 10
The nasal cavity warms the air to body temperature, moistens it with mucus so it doesn't dry out delicate lung tissue, and filters out dust and pathogens using mucus and tiny hairs called cilia.
Biology · L3 · Respiratory Anatomy
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Biology · L3 · Respiratory AnatomyFlashcards10 cards
What is negative pressure breathing?1 / 10
Negative pressure breathing is the mechanism mammals use to inhale: the diaphragm and intercostal muscles enlarge the thoracic cavity, which drops the air pressure inside the lungs below atmospheric pressure, so air flows in to equalize it.
Biology · L3 · Breathing Mechanics and Gas Exchange
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Biology · L3 · Breathing Mechanics and Gas ExchangeFlashcards9 cards
What do the salivary glands secrete, and where?1 / 9
Saliva, released into the mouth. It contains the enzyme salivary amylase, which begins breaking down starch into maltose.
Biology · L3 · Digestive Organs and Secretions
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Biology · L3 · Digestive Organs and Secretions